As pointed out in the specification of one of the applicants earlier U.S. Pat. No. 4,059,968, assigned to the same assignee as the present invention, the H. A. Phillips & Co., Chicago, Ill., the assignee has long been a leader in the design, development and installation of industrial type refrigeration systems. H. A. Phillips & Co. has been a pioneer in recirculating systems and numerous patents have issued to it covering these systems over the past thirty years. These include Phillips U.S. Pat. No. 2,570,979; Phillips U.S. Pat. No. 2,589,859; Phillips U.S. Pat. No. 2,641,281; Richards, Pat. No. 2,841,962; Richards et al. U.S. Pat. No. 2,871,673; Ross Pat. No. 2,966,043; Ross Pat. No. 3,315,484; and the aforementioned Ross patent.
In each of these recirculating systems, as well as in other recirculating systems presently in use, the system disclosed in the Garland U.S. Pat. No. 4,151,724, for example, relatively high pressure flash gas which is formed in the system receiver is returned to the normal system compressor operating at a lower pressure level than the receiver. (The normal system compressor must compress this flash gas from low pressure up to condensing pressure.) Such systems have been efficient enough for the low cost energy of the past. However, the rapidly increasing cost of energy coupled with the normal propensity of refrigeration systems to use energy at a prodigous rate, as well as wider use of such systems, have caused the industry to seek more economical systems for several years.